1. Field of the Invention
This invention relates to a semiconductor device having a protruding electrode that is disposed on a pad electrode and its manufacturing method.
2. Description of the Related Art
In a conventional semiconductor device for surface mounting, a bump is formed on a pad electrode. FIG. 10 is a plan view showing a pad portion of the semiconductor device. FIG. 11 is a cross-sectional view of a section B-B shown in FIG. 10. In the conventional pad portion, it is avoided to place an incompletely filled via hole 55 under an exposed portion 56a of the pad electrode 56, which is exposed in an opening 57a in a protection film 57, as shown in the figures.
The reason to avoid it is that placing the incompletely filled via hole 55 under the exposed portion 56a of the pad electrode 56 causes problems that an inside of the incompletely filled via hole 55 is corroded by chemicals used in etching a protection film 57 for passivation and left in a vacancy that is caused in the via hole 55 as will be described later, or plating solution used in forming the Au bump 59 by a plating method and left in the vacancy, and that cracks are caused in an interlayer insulation film 54 that surrounds the via hole 55 depending on an amount of a pressure imposed on the semiconductor device in a COG (Chip On Glass) mounting, if the incompletely filled via hole 55 is placed under the exposed portion 56a of the pad electrode 56.
Therefore, placing the incompletely filled via hole 55 under the exposed portion 56a of the pad electrode 56 is avoided and the incompletely filled via hole 55 is formed in the interlayer insulation film 54 on a first layer metal wiring 53 in a region adjacent the exposed portion 56a of the pad electrode 56.
When an Au bump 59 is formed, a peripheral portion 59a of the Au bump 59 is jutted out by an amount corresponding to a height of a step 58 of the protection film 57 at a periphery of the exposed portion 56a of the pad electrode 56, as shown in FIG. 11.
This kind of semiconductor device is disclosed in Japanese Patent Application Publication Nos. H07-161722 and 2003-017521, for example.
Since placing the incompletely filled via hole 55 under the exposed portion 56a of the pad electrode 56 is avoided because of the reasons described above, there is a problem that a region under the pad electrode 56 is not utilized efficiently.
Also, there is a problem that a large amount of force is applied locally to a semiconductor substrate 51 under the Au bump 59 when the semiconductor device is mounted, since the peripheral portion 59a of the Au bump 59 is jutted out in the conventional semiconductor device. Particularly when a semiconductor element 52 is formed in the semiconductor substrate 51 under the Au bump 59, there is a problem that the large amount of force is applied to the semiconductor element 52.